1. Field of the Invention
This invention relates to rubber power transmission belts of the V-type, and particularly to a rubber V-belt having one or more plies of a fabric band covering the exterior driving surfaces of the belt.
2. Description of Related Art
Covered or banded power transmission V-belts are normally constructed with an outer layer of rubber or other polymer impregnated fabric surrounding the belt core. The cover provides a number of functions, including protecting the belt from environmental elements, controlling the frictional characteristics of the belt, and resisting wear of the belt as it contacts the sheaves (pulleys) in a V-belt drive. These “full cover” V-belts are typically manufactured so that one edge of the outer layer of fabric laps over the other edge. This lap runs the entire length of the belt. Some belts have multiple layers of fabric. Belts with two layers of fabric can have laps that are stacked on top of one another. A typical prior art banded V-belt construction is shown in FIG. 7 of the drawings in which inner band 11 is lapped at the top surface of the belt at 15, and outer band 13 is lapped at the top surface of the belt at 17, forming stacked laps. These laps create a thickness variation in the core of the belt that cause the layer of tensile members 19 to become distorted from its normal horizontal orientation.
Because the tensile cord of the load-carrying section is responsible for transmitting power in the belt, a distortion in the cord line results in uneven distribution in the tensile member. This uneven loading decreases the belt's ability to transmit power when compared to a belt that has uniformly loaded cord. Furthermore, the prior art belt, which may have a lap located on the upper most or lower most surface of the belt, exhibits increased bending resistance. Such an increase in bending resistance, particularly in drives utilizing relatively small diameter sheaves, results in reduced belt life.
There is a need for a banded V-belt construction that provides optimal frictional properties for the driving surfaces of the belt, offers maximum protection to the embedded tensile cords while minimizing the use of fabric material to limit bending resistance, and avoid the use of laps that would otherwise lead to distortion in the cordline and uneven load distribution in the tensile member.